July Bonnie Brooks. Minnesota Pollution Control Agency Environmental Analysis and Outcomes Division

Transcription

1 July 2015 Bonnie Brooks Minnesota Pollution Control Agency Environmental Analysis and Outcomes Division

2 Remediation Program* Soil Reference Value (SRV) Revision Timeline Draft SRV Values & Technical Support Documents (TSD) Released Stakeholder Review and Comments on Draft SRV and TSD (comments to MPCA by 12/15/14) MPCA Review of Stakeholder Comments MPCA Responses to Stakeholder Comments Draft SRV, TSD, & Background Values Released MPCA & Stakeholder Meeting Stakeholder Review and Comments on Draft SRV, TSD and Background Values (comments to MPCA by 9/30/15) Draft SRV Related Program Specific Guidance Released MPCA Review of Stakeholder SRV and BTV Comments Final SRV, TSD, Background Values, & Program Specific Guidance Released All Final SRV, TSD, Background Values & Program Specific Guidance are in Effect Starting January 1, 2016 Stakeholder Review and Comments on Program Specific Guidance Documents (comments to MPCA by 11/30/15) Additional MPCA & Stakeholder Meetings as Needed or Upon Request MPCA Review of Stakeholder Program Specific Guidance Comments * Superfund, Site Assessment, VIC, RCRA Cleanup 2

3 Periodically revised to incorporate new Methodology Exposure parameters Toxicity values Chemical specific parameters Not in response to any specific incident, project or occurrence 3

4 Methodology EPA Superfund methodology Addition of mass limit volatilization factor Exposure Parameters 2014 EPA Superfund recommendations Minnesota specific modifications Toxicity values More recent values used if appropriate Chemical specific parameters EPA Superfund hierarchy 4

5 SRV Technical Support Document (TSD) DRAFT COMPLETED How the SRVs were derived and their intended use SRV Spreadsheet DRAFT COMPLETED SRVs applicable to any site in Minnesota SRV Spreadsheet - Site Specific DRAFT COMPLETED Used to derive SRVs applicable to a specific site Soil Investigation Guidance TO BE DRAFTED VIC, Superfund, RCRA program Specific Guidance SRVs are one of the tools used 5

6 SRV Revisions - MPCA Remediation Division Staff participation in work groups Consultation with other staff and staff review of documents Environmental Outcomes & Analysis Division Remediation risk assessor participation in work groups Consultation with other staff and other risk assessors/toxicologist review of documents Consultation and review of documents MDH MDA EPA USGS (inorganics in BTV documents only) 6

7 VIC, Superfund, RCRA cleanup sites SRVs are a screening tool NOT intended to be used as Cleanup Values Responsible or voluntary parties can Chose to derive site specific SRVs for clean up values Chose to use state wide SRVs as cleanup values 7

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9 Human exposures to soil on land NOT ecological NOT sediments Soil Exposure Routes Ingestion Dermal Contact Inhalation Particulates in surface soil Particulate Emission Factor Volatilization from soil at depth Volatilization Factor (standard and mass limit) 9

10 Exposure Frequency Receptor type based on soil land use category Residential/Recreational Commercial/Industrial Soil exposure route Ingestion Dermal Inhalation via fugitive dust Inhalation via vapors Type of contamination present VOCs Non-VOCs 100 frozen and snow covered days per year eliminated from some exposure routes 10

11 Exposure Route VOC Non-VOC Ingestion Dermal Contact Inhalation Fugitive Dust Inhalation Vapors Eliminate 100 days/year Although ingestion exposure will occur both indoor and outdoor, VOCs will not be present in indoor dust due to their volatile nature NOT included for VOCs Dermal contact is not considered to be a significant route of exposure for VOCs due to their volatile nature NOT included for VOCs Inhalation of fugitive dust is not considered to be a significant route for exposure for VOCs due to their volatile nature Eliminate 100 days/year Vapors are not expected to be present outdoors when the ground is frozen and snow covered greater than 1 inch Do NOT eliminate 100 days/year Ingestion exposure will occur both indoor and outdoor and non-vocs will be present in indoor dust Eliminate 100 days/year Dermal contact is considered to only be a significant route of exposure outdoors and will not occur when the ground is frozen and snow covered greater than 1 inch Eliminate 100 days/year Fugitive dust is not expected to be present outdoors when the ground is frozen and snow covered greater than 1 inch Eliminate 100 days/year Vapors are not expected to be present outdoors when the ground is frozen and snow covered greater than 1 inch 11

12 Ingestion Rate Previous ingestion adjusted to account for frozen days and snow covered days New ingestion rate does not consider frozen and snow covered days since this is considered in exposure frequency 12

13 Standard volatilization factor Contamination right below ground surface Infinite source may violate mass balance considerations Uniform rate of volatilization based on Infinite source Henry s Law specific to a contaminant 13

14 Mass limit volatilization factor Contamination right below ground surface Finite source based on thickness of contamination Uniform rate of volatilization based on Finite source size 14

15 Volatilization Factors Eliminate violation of mass balance considerations 2 SRVs derived 1 using standard volatilization factor 1 using mass limit volatilization factor SRV with highest value used Example Chemical X SRV using standard VF = 100 mg/kg Chemical X SRV using mass limit VF = 200 mg/kg SRV is set at 200 mg/kg 15

16 Mass limit volatilization factor Net increase for impacted VOCs Exposure parameters Residential/Recreational SRVs Net slight decrease Commercial/Industrial SRVs Net increase Toxicity Values & chemical specific parameters Contaminant specific 16

17 SRVs potentially below soil background levels? Aluminum Arsenic Barium Chromium Cobalt Iron Thallium Vanadium Benzo[a]pyrene (BaP) equivalents TCDD (2,3,7,8-Tetrachlorodibenzo-p-dioxin) equivalents 17

18 Evaluation to determine if SRVs are below soil background levels Establish a Background Threshold Value (BTV) Estimate of the background level in soil Background Amount of a chemical that is present in soil that is NOT due to local anthropogenic sources such as a release 18

19 Inorganics: aluminum, arsenic, barium, chromium, cobalt, iron, thallium, vanadium USGS s 2013 Soil Survey 137 samples from Minnesota USGS vs. EPA analytical methods USGS - aggressive digestion EPA - less aggressive digestion Results in different concentrations Specific chemical Geological characteristics of the soil Differences NOT consistent across Minnesota 19

20 Difference between USGS and EPA s method? Re-analyze 45 samples using EPA method Data USGS complete 137 sample dataset EPA reanalyzed 45 sample dataset BTV Evaluation Differences in concentrations across Minnesota Outliers using USGS s full 137 sample dataset Are background concentrations higher than SRV? Differences between results of 2 methods Establish BTV if necessary 20

21 How was a BTV established? Complete USGS 137 sample dataset EPA s ProUCL software Upper Tolerance Limit (UTL) What is a UTL95-95? 95% confidence limit of the 95 th percentile of the dataset Why a UTL? Large number of comparisons to BTV False positive and negative errors rates minimized Some BTVs were established using a lower percentile All BTVs used a 95% confidence limit 21

22 Difference between USGS & EPA methods varies by Specific inorganic Geology at sample site Inorganic Minimum Difference Maximum Difference Upper Percentile Difference Aluminum -95% -67% -70% Arsenic -75% 39% -1% Barium -95% -65% -71% Chromium -84% -48% -63% Cobalt -56% 21% -19% Iron -65% -2% -32% Thallium -79% -35% -55% Vanadium -76% -11% -52% 22

23 Inorganic Soil Land Use Category EPA Method Value mg/kg Source USGS Method Value mg/kg Source Aluminum Arsenic Barium Chromium III Chromium VI Cobalt Iron Thallium Vanadium Res/Rec Chronic 59,000 BTV, UTL95-95 from USGS dataset Com/Ind Chronic 100,000 Com/Ind chronic SRV Res/Rec Acute 9 BTV, UTL95-95 from USGS dataset Res/Rec Chronic 9 BTV, UTL95-95 from USGS dataset Com/Ind Chronic 9 BTV, UTL95-95 from USGS dataset Res/Rec Acute 250 Res/Rec acute SRV Res/Rec Chronic 3,000 Res/Rec chronic SRV Com/Ind Chronic 35,000 Com/Ind chronic SRV Res/Rec Chronic 23,000 Res/Rec chronic SRV Com/Ind Chronic 100,000 Com/Ind chronic SRV Res/Rec Chronic 11 Res/Rec chronic SRV Com/Ind Chronic 57 Com/Ind chronic SRV Res/Rec Chronic 13 BTV, UTL95-95 from USGS dataset Com/Ind Chronic 67 Com/Ind chronic SRV Res/Rec Chronic 30,000 BTV, UTL95-90 from USGS dataset Com/Ind Chronic 100,000 Com/Ind chronic SRV Res/Rec Chronic Site specific BTV Com/Ind Chronic 2.3 Com/Ind chronic SRV Res/Rec Chronic 121 BTV, UTL95-95 from USGS dataset Com/Ind Chronic 121 BTV, UTL95-95 from USGS dataset Determining site specific background is always an option 23

24 Map of arsenic background concentrations in Minnesota from USGS dataset Determining site specific background is always an option 24

25 Organics: BaP equivalents, TCDD equivalents Other states data Data specific to other states reflecting ambient levels Inorganic Soil Land Use Category 1 EPA Method Value 2 mg/kg Source 3 BaP Equivalents TCDD Equivalents Res/Rec Chronic 1 BTV, available data Com/Ind Chronic 14 Com/Ind chronic SRV Res/Rec Chronic 4.0E-06 Res/Rec chronic SRV Com/Ind Chronic 2.0E-05 Com/Ind chronic SRV 25

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27 Applicable to VIC, RCRA & Superfund sites only Derived using SRV Spreadsheet Site Specific Requires approval of project manager & risk assessor Ability to modify exposure parameters Example: Hazard Quotient (HQ) Purpose present a range of potential risks Example: Exposure frequency Purpose reflect site specific conditions Site Specific SRV Exposure Parameter Modifications Table in SRV TSD, Table B-1 27

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29 Questions? 29